Aftermarket Gauges: Everything You Need To Know About

Stock or OEM Instrument Clusters

Regardless of the type of vehicle you drive, your stock instrument cluster likely tells you some important information on a modern vehicle. That is, you probably have a speedometer and odometer. Your vehicle will also come with a fuel gauge, and usually a temperature and oil pressure gauge. This has not always been true, however. In the past, many vehicles only featured warning lights that illuminated when something went wrong. This was very typical of cars in the 60’s to the late 80’s, many of which people are restoring or modifying today.

While OEM instrument clusters have come a long way in recent years, they are far from perfect. In fact, most gauges only tell you a bit of information about your vehicle and when vehicles are modified for performance, often times, more information is needed for the driver.

For this article, we will cover both aspects of aftermarket gauges, and how to choose them – both for newer vehicles and vintage.

Upgrading Vintage Vehicles

As stated before, many vintage vehicles, especially those from 1960-1990, used lights to indicate low oil pressure, or high temperature, which left a lot to be desired. Because of this, many car enthusiasts added a “triple set” of gauges where they could, which gave the car 3 gauges that weren’t found on them at the time – Oil Pressure, Coolant Temperature, and a Voltage or Ammeter gauge. These same 3 gauges are still sold together today, and along with a Tachometer is usually all that’s needed to upgrade a vehicle of this era and give the driver a full-scope on what’s going on under the hood.

When choosing aftermarket gauges for these vehicles, usually the most important question is whether or not you want these gauges to be mechanical, or electrical.

Mechanical and Electrical Gauges

Mechanical gauges have been around for nearly a century. These gauges have a direct connection to what’s being measured. That is, a mechanical gauge may use an oil line that allows the gauge to directly measure oil pressure, or, a temperature probe that is screwed directly in a coolant passage.

On the other hand, Electric gauges function differently. Rather than featuring a direct connection, electric gauges operate using a sensor, or sender, which is screwed or plumbed directly into what’s being measured. While this is essentially the same as the mechanical device, the difference is that this sensor then picks up and sends the information via an electrical wire to the gauge, where the gauge then displays the information.

The difference in your decision depends on a few factors. Keep in mind that on either gauge, the lighting to illuminate the gauge at night will always require an electrical signal and ground, so regardless of which design you use, you will still be doing electrical work.

A Mechanical gauge will have less wires though, but you will need to run the materials through the firewall and dash that allow the gauge to operate – usually tubing or piping. The benefit though is that mechanical gauges tend to be slightly cheaper, as they don’t require the purchase of the sensor or sending unit to pick up the signal and make the gauge operate. With either gauge, you will need to know several specifics on the vehicle you are working on :

• Do you have an accessible port to thread in and attach the sender or mechanical tap for the gauge? What size is it? Many gauges come with or you can purchase an installation kit that has adapters. Make sure you research all that you will need carefully.
• Is the sender for an electrical gauge available for the size port you need on your vehicle’s engine? Or, is an adapter available to size correctly?

In the past, automotive enthusiasts believed mechanical gauges to offer better accuracy than their electrical counterparts. That is no longer the case. Provided you purchase an electrical gauge from a reliable manufacturer, you can likely assume it is as accurate as a mechanical alternative.

Adding Gauges on Modern Vehicles

On modern vehicles, or vehicles in the “Tuner” or Diesel truck era, there are several aftermarket gauges that are very popular. For vehicles with a Turbocharger, adding a boost gauge is popular, and certainly crucial if the car is being tuned or modified from its original factory boost pressures. Oddly, many cars during the dawn of Turbocharging in the 1980’s had boost gauges, but today, most vehicles are not equipped with them. Cars not only benefit from a Boost Gauge, but Diesel trucks as well, as many of these owners are modifying for performance by adding more fuel, and more boost.

Another gauge that is gaining in popularity with Diesel trucks is an exhaust temperature gauge, or EGT gauge. With Diesel Trucks, when you add more fuel, more boost, and couple that with a hard working truck that tows, exhaust temperatures can rise rapidly. Temperatures nearing 1200 degrees in a high boost / high load situation can lead to catastrophic failure. Because of this, adding an EGT gauge to a Diesel Truck, so the driver can monitor temps is vital.

Lastly, and growing in popularity with all gas-fed vehicles is the air/fuel gauge. In order for proper, efficient combustion, a proper mix of air and fuel must be had. The science on this is known as Stoichiometry, or “Stoich” for slang, and for gasoline engines, the Stoichiometric measurement for proper combustion is 14.7 parts air to 1 part fuel. From there, tuners will attempt to lean or richen the mixture slightly to find the perfect balance between the modification parts, turbo or supercharger boost (if applicable), the fuel, and performance the engine is making – all while attempting to keep it safe and from blowing up! To do this, a real-time air/fuel gauge is often added to monitor exactly what is going on with the mixture.

Installation

After you have decided on the mechanical or electrical gauge, or what varieties of gauges, styles, and lighting options you wish to add, you are ready to move on to installation. The first task you must accomplish is deciding where to locate your new aftermarket gauge. Picking a spot that allows you to easily read the gauge without obstructing your road view makes sense. One common item is the gauge “pillar-pods”, which mount a gauge or series of gauges on the driver’s side pillar in between the windshield and the driver’s door. Many other aftermarket companies and gauge companies make pods that can be added to the dash, under the dash, or even sit right inside the gauge cluster itself.

Keep in mind being careful when drilling into the dashboard itself, and remember that wherever you install your gauges, you will need to run a multitude of wiring to that location. Generally speaking, all gauges, especially electrical ones, are going to need 2 sources of voltage from somewhere – one, they will need a 12V source from the headlight switch that is 12V when either the parking or headlights are turned on. This source will power the lighting on your gauges, to operate when the headlights or parking lights are turned on. Two, you will need a 12V ignition source, meaning, a wire than has 12V when the ignition key is in the RUN position. Finally, the lighting circuit, and often the gauge itself, will need a ground wire as well.

Final Thoughts on Aftermarket Gauges

Aftermarket gauges are often an effective strategy for supplementing your vehicle’s stock instrument cluster. Whether you want to get as much performance as possible out of your machine or simply want to minimize your chances of a catastrophic mechanical failure, installing an aftermarket gauge may be the right approach.

As with other components, aftermarket car gauges, vary in reliability and quality. If you have decided to install one on your vehicle, be sure you choose a well-known and highly rated manufacturer. Also, when installing your new gauge, take care not to damage existing systems. With the right tools, a quality gauge and a bit of effort, though, you can likely get the information you need to get the most out of your vehicle. You can get the parts you need at your local AutoZone Store. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.